1. Technical Field
Various embodiments relate generally to an operating circuit controlling device, a semiconductor memory device and a method of operating the semiconductor memory device.
2. Related Art
Semiconductor memory devices are typically categorized into volatile or non-volatile memory devices.
Volatile memory devices are considered to operate in high write and read speeds, but they are unable to retain the stored data when the power is off. Non-volatile memory devices operate at relatively lower write and read speeds, but they can retain the stored data regardless of power on/off conditions. Examples of the non-volatile memory include Read Only Memory (ROM), Mask ROM (MROM), Programmable ROM (PROM), Erasable Programmable ROM (EPROM), Electrically Erasable and Programmable ROM (EEPROM), flash memory, Phase-change Random Access Memory (PRAM), Magnetic RAM (MRAM), Resistive RAM (RRAM) and Ferroelectric RAM (FRAM). Flash memories are categorized into NOR or NAND type.
Flash memories enjoy the advantages of both RAM and ROM. For example, flash memories can be freely programmed and erased similar to RAM. Similar to ROM, flash memories can retain the stored data even when they are not powered. Flash memories have been widely used as the storage media of portable electronic devices such as mobile phones, digital cameras, personal digital assistants (PDAs), and MP3 players.
Sudden drop of the voltage applied to a semiconductor memory device may occur at unpredictable times for various reasons, and this can cause problems in the semiconductor memory device.